Ferroelectric Polarization Reversal Characteristics Of The Pzt Films

Lead zirconate titanate has superior ferroelectric, pyroelectric, and piezoelectric characteristics, and it has been studied widely since 60'of last century. Especially, PZT is one of most promising ferroelectric materials for non-volatile random access memories because of high dielectric constant, high remnant polarization and high curie point. In this work, the influences of thickness and grain size on ferroelectric, polarization switching current have been studied in experiments and theoretical analyses. We have investigated the film orientation mechanism in the heat treatment processing. The films with different orientation have been obtained. Meanwhile, we discussed the influence of orientation on the ferroelectric and fatigue properties. Pb(Zr_0.55Ti_0.45)O₃ thin films were prepared on the Pt(111)/Ti/SiO₂/Si(100) substrates by radio frequency magnetron sputtering method, then the films were annealed at various temperature by a rapid thermal annealing process in order to obtain different grain sizes. The experiment results showed that the grain size strongly influenced the ferroelectric properties of PZT thin films. With the grain size increasing, the saturated polarization was enhanced, while the coercive field increased firstly and then decreased. One possible explanation could be that the mechanism of polarization switching have changed with the gain size increasing, the domain structure changed from a single domain state to a multi-domain state. A preliminary model based on modified Ising model been given an explanation for the gain size effect on ferroelectric properties. The switching current of ferroelectric thin film has been investigated by using the Ishibashi-Takagi theory. Considering the combined effects of both categoriesⅠand categoriesⅡon the switching current, we formulated a new model. We have compared it with the experiment results, the fitting results indicated that the model was acceptable. The influence of electrical field, temperature, and gain size on switching current was also discussed. Using rapid thermal annealing process (RTA) and conventional furnace annealing process (CFA), highly (100)-and (111)-oriented PZT thin films have been obtained successfully through the control of processing parameters during post-anneal treatments. In addition, the crystallization mechanism of the film with different...